The present invention relates to disposable underpants having such a shape that a waist-opening and a pair of leg-openings are provided and left and right sides are bonded in advance, and including an absorbent core which has an excellent shape retention and is easily producible, and a method for continuously producing such disposable underpants.
Since disposable underpants commercially available at present are produced under a condition that a user walks and makes physical motions while wearing them, an absorbent core is required to have a high shape retention.
Accordingly, in the prior art, a thermoplastic resin in the form of fibers and particles is mixed as a shape retaining material in addition to pulp fibers and super absorbent polymer, particles. More specifically, if such an absorbent core is heated, this thermoplastic material is melted to adhere to the pulp fibers and the super absorbent particles. Thus, the pulp fibers are adhered to each other or adhered to the super absorbent polymer particles after a heating treatment, thereby improving the shape retention of the absorbent core. Further, the soft and bulky absorbent core can be effectively maintained thin by the mixing of the thermoplastic resin and the heating adhesion treatment.
However, if the thermoplastic resin fibers, particles, etc. are not uniformly dispersed, i.e. concentrate in several locations without being uniformly dispersed in the absorbent core, this causes such a problem that portions of the absorbent core where the thermoplastic resin is concentrated hinder the dispersion and permeation of urine and/or prevent the super absorbent polymer particles from swelling upon absorbing water, thereby reducing an absorbing speed of liquid bodily wastes.
In order to produce the above absorbent core, an oven for heating an absorbent core obtained by laminating fibers needs to be prepared. A circulating hot blast oven is generally used as such an oven. However, it is difficult for the hot blast to reach the inside of the absorbent core obtained by laminating fibers to a thickness of about 10 mm, and the absorbent core has to be passed through the oven over an extended time in order to heat it until the inside thereof reaches a melting temperature of the thermoplastic resin. In order to extend the passing time in the oven, the oven itself may be enlarged. However, this results in a large-scale facility and is disadvantageous in terms of production cost. As a result, the passing speed of the absorbent core in the oven has to be slowed, which stands as a hindrance to an improvement in production efficiency.
On the other hand, the conventional disposable underpants are made of nonwoven fabric and others, also elastic members in the form of threads or strips (made of natural rubber, polyurethane, polyolefin elastomer, etc.) are provided near and around the waist-opening and the pair of leg-openings. Even if stretchable gathers are formed only around these openings, the disposable underpants cannot be worn while ensuring a sufficient sealability. Particularly, the disposable underpants provided with a bulky absorbent core does not fit a user at the lower abdomen and the buttocks and bulges out there. For example, if a person having a light problem of incontinence wears a usual garment (trousers or skirt) over disposable underpants, the disposable underpants cause his or her waist line to bulge out, which is not a preferable appearance. In view of the user""s psychology, it is naturally demanded to improve the disposable underpants to have such a shape with which nobody would notice that the user is wearing them. However, if a small absorbent pad is used so that nobody would notice, a urine leak may occur. Even if no urine leak actually occurs, users have refrained from going out due to an anxiety that they might have a urine leak.
A first object of the present invention is to produce disposable underpants provided with an absorbent member which is so constructed as to have a good shape retention without mixing thermoplastic resin fibers and particles into pulp fibers and heating them. A second object of the present invention is to provide disposable underpants which fit a user sufficiently and is unlikely to let other people notice that the user is wearing them.
The present invention is directed to disposable underpants having one waist-opening and a pair of leg-opening, having-elastic members provided near the edges of the waist-and leg-openings and having the opposite sides thereof bonded, comprising an outer sheet and an inner absorbent member, wherein:
the outer sheet is provided with a waist elastic member, leg elastic members and a fitting elastic member provided between the waist elastic member and the leg elastic members, the fitting elastic member being comprised of a plurality of thread-like elastic materials in parallel with the waist elastic member,
the inner absorbent member includes a permeable top sheet, an impermeable back sheet and an absorbent core accommodated between the top and back sheets, and
the absorbent core includes an upper layer made of a mixture of pulp fibers and super absorbent polymer particles, an intermediate layer provided with a first nonwoven fabric, and a lower layer made of a mixture of pulp fibers and super absorbent polymer particles, the intermediate layers being adhered to the upper and lower layers by an adhesive.
Further, a method for continuously producing disposable underpants comprises the steps of:
adhering waist elastic members, leg elastic members and fitting elastic members to a continuous web of an outer sheet,
producing absorbent cores by adhering upper layers made of a mixture of pulp fibers and super absorbent polymer particles and lower layers made of a mixture of pulp fibers and super absorbent polymer particles to the upper and lower surfaces of first nonwoven fabric of intermediate layers by an adhesive,
producing inner absorbent members using the absorbent cores,
forming a laminated assembly by adhering the inner absorbent members at specified intervals onto the continuous web of the outer sheet having the respective elastic members adhered thereto,
folding the laminated assembly in two with the inner absorbent members faced inward,
providing cut-away portions for the leg-openings in the laminated assembly folded in two,
bonding the opposite sides of the laminated assembly folded in two, and
separating the laminated assembly having its opposite sides adhered at specified intervals to form the individual disposable underpants.